The present invention relates to an inductance means. The invention also relates to an integrated circuit chip including such an inductance means.
A circuit component is frequently described as having an impedance Z with a resistive part and a reactive part. In other words a component has a resistance R and a reactance X. The reactance X may include an inductive component, rendering the impedance of the component inductive and resistive.
The article "SiIc-Compatible Inductors and LC Passive Filters" (IEEE Journal of Solid-State Circuits, Vol. 25, No. 4, 1990) by N. M. Nguyen and R. G. Meyer, discloses a square spiral inductor which is fabricated of aluminium on a silicon substrate. The disclosed inductor having an inductance of 9.7 nH also had a series resistance of 15.4 Ohm and a maximum Q-value below 4 at 0.9 GHz. Hence, the performance of the disclosed inductor is limited by the metal resistance.
The article "Microwave Inductors and Capacitors in Standard Multilevel Interconnect Silicon Technology" (IEEE Transactions on Microwave Theory and Technique, Vol. 44, No 1 January 1996) discloses a spiral inductor on a silicon substrate. The disclosed inductor has four turns, and thicker metal wires which are realized in standard 0.8 micrometer BiCMOS silicon technology by connecting multiple metal layers with dense via arrays. The disclosed spiral inductor has three metal levels mutually connected with a via array, and an underpass at a lowest of four metal levels provided in the silicon substrate. The article reports an estimated Q-value of 9.3 at 4 GHz for such an inductor.